Method and apparatus for lens mounting



Oct. 12, 1965 o. T COSTELLO METHOD AND APPARATUS FOR LENS MOUNTING Filed March 15, 1962 INVENTOR.

OWEN T. COSTELLO BY a Q M ATTORNEY United States Patent M 3,210,841 METHDD AND APPARATUS FQR LENS MOUNTKNG @Wen Costeilo, Philadelphia, Pa, assignor to the United States or" America as represented by the Secretarry of the Army Filed Mar. 1.5, 1962, Ser. No. 180,057 3 Qlaims. (Ci. 29-5ill) (Qranted under Title 35, US. Code (1952), see. 266) The invention described herein may be manufactured and used by or for the government for governmental purposes Without the payment to me of any royalty thereon.

This invention relates to a method and apparatus for mouting a lens in a cylindrical holder and has for an object to produce a more nearly moistureproof mounting for an optical lens which is also free from the danger of fracture or clouding of the lens due to local unbalanced internal stresses within the lens.

For many years efiorts have been made to obtain a moistureproof mounting for a lens. One expedient tried was to exhaust the air within the tube. Another suggestion has been to have helium within the lens tube to keep out moisture.

it has now been discovered that by pressing the lens element against a yieldable moistureproof material and maintaining such a material always under pressure but below a pressure likely to fracture the lens, that best results so far have been obtainable. A lens may cloud due to unbalanced local stresses within the glass below a fracture stress, but these have now been kept from forming by a method and apparatus so simple that it is no longer necessary to subject a lens to a time consuming test with a polariscope to determine the presence of objectionable internal stresses and strains within a lens.

Referring to the drawings:

FIG. 1 illustrates an embodiment of this invention.

FIG. 2 shows a preferred embodiment.

A lens of optical glass is mounted in a holder 11 and this holder may be rotated by a lathe chuck 12 or in any convenient manner. The lens 10 is of any well known type and contour and may be of 1 or 2 or more elements cemented together in ways well known in the art. Between a usual shoulder 14 against which the lens is pressed, is placed a pad or sealing ring 1.3 of some yieldable moistureproof material such as polyethylene or similar material. Some pressure applicator 15 applies pressure axially to the lens and longitudinally of the holder. The end 16 of applicator contiguous the lens is usually shaped to conform to the contour of the lens outer surface. Between the end 16 and body 15 of the applicator is an antitriction or ball bearing 17 and a spring 18 which may be compressed to provide the desired pressure by adjustment of the body 115 of the applicator toward the end 16 and lens 10. A window in the body 15 of the applicator provides a suitable place for graduations 20 on either the stem 19 or on the body 15 to indicate the degree to which the spring 18 is compressed. A spinning tool 21 is provided with a roller 22 for bending over a flange 24 for retaining the lens clamped under pressure upon the sealing ring 13. An indicator 23 of the degree of pressure applied to the spinning over of flange 24 is provided as in FIG. 1.

The same apparatus is used in FIG. 2 as in FIG. 1 except that a retaining ring 25' is provided between the spun over flange and the lens. This ring 25 is also of a yieldable moistureproof material which assists the sealing 13 in keeping moisture from entering the lens holding tube ill.

in operation the rate of rotation of the lens holder is not critical but the end portion 16 of the pressure ap- I lifil ltl li Patented @ct. l2, 1:265

plicator should rotate with the lens in order not to scratch or abrade a surface of the lens. The surface of the en 16 touching the lens surface should be of a deformable plastic rather than metal. In the spinning operation the pressure applied to the spinning tool should be less than that applied to the applicator 15. The reason is because it has been found the unbalanced local internal stresses are largely reduced when in spinning the pressure applied to the spinning tool is substantially less than that appiied axially by the applicator 15. With one material for the lens it has been found desirable to apply 60 pounds pres sure axially to the lens and 50 pounds to the spinning tool for bending down the flange 24. The reason for this relationship is not known for a certainty but the result is an advantage for the reason ascribed.

I claim:

It. in a method for mounting an optical glass lens in a moistureproof holder comprising rotating said holder about a longitudinal axis, pressing said lens against a shoulder in said holder, and spinning a peripheral flange over an edge of a lens, the combination therewith of the improvement for reducing the danger of fracturing a lens, the danger of moisture collecting in said holder, and the danger of local unbalanced stress within a lens, said improvement including inserting a pad of yieldable moistureproof material between said shoulder and lens to reduce the danger of moisture getting into said holder past a lens, pressing said lens axially against said yieldable pad and shoulder with a pressure below that likely to fracture a lens, and spinning over said flange with a pressure less than that of said axial pressure on said lens while rotating the lens.

2. in an apparatus for moistureprooily mounting a lens of optical glass in a cylindrical holder comprising means for rotating said holder about a longitudinal axis, means for axially pressing said lens against a shoulder in said holder, and means for spinning a flan e over an outer peripheral edge of a lens, the combination therewith of the improvement for reducing the danger of moisture passing into said holder around said lens, for reducing the danger of a lens being clouded due to unbalance-d and local internal stress within the lens, said improvement including means for indicating the axial pressure applied to said lens during its rotation, means for indicating the pressure applied to a spinning tool for said flange whereby said spining pressure may be kept below said axially applied pressure and both pressures safely below that likely to fracture a lens.

3. Apparatus according to claim 2 in which a roller type bearing is in said lens axial pressing means and a roller type bearing is in said spinning means.

References Eited by the Examiner UNITED STATES PATENTS WHITMORE A. WiLTZ, Primary Examiner.

JEWEL H. PEDERSEN, JOHN E. CAMPBELL,

Examiners. 

1. IN A METHOD FOR MOUNTING AN OPTICAL GLASS LENS IN A MOISTUREPROOF HOLDER COMPRISING ROTATING SAID HOLDER ABOUT A LONGITUDINAL AXIS, PRESSING SAID LENS AGAINST A SHOULDER IN SAID HOLDER, AND SPINNING A PERIPHERAL FLANGE OVER AN EDGE OF A LENS, THE COMBINATION THEREWITH OF THE IMPROVEMENT FOR REDUCING THE DANGER OF FRACTURING A LENS, THE DANGER OF MOISTURE COLLECTING IN SAID HOLDER, AND THE DANGER OFF LOCAL UNBALANCED STRESS WITHIN A LENS, SAID IMPROVEMENT INCLUDING INSERTING A PAD OF YIELDABLE MOISTUREPROOF MATERIAL BETWEEN SAID SHOULDER AND LENS TO REDUCE THE DANGER OF MOISTURE GETTING INTO SAID HOLDER PAST A LENS, PRESSING SAID LENS AXIALLY AGAINST SAID YIELDABLE PAD AND SHOULDER WITH A PRESSURE BELOW THAT LIKELY TO FRACTURE A LENS, AND SPINNING OVER SAID FLANGE WITH A PRESSURE LESS THAN THAT OF SAID AXIAL PRESSURE OF SAID LENS WHILE ROTATING THE LENS. 